GPX Viewer PRO supports starting/pausing, stopping and adding waypoints by automation with Tasker app - This how to will explain how this could be automated with Tasker app:

Send Intent [ 
  Action: android.intent.action.RUN
  Cat: None
  Mime Type:
  Data:
  Extra: android.intent.extra.TEXT:TRACK_RECORDING_ACTION_START_PAUSE
  Extra:
  Extra:
  Package: com.vecturagames.android.app.gpxviewer.pro
  Class:
  Target: Activity ]

1. During track recording open left main menu.
2. Tap on Settings button.
3. In Settings tap on Track recording button.
4. Then scroll down and disable Automatically delete tracks after export checkbox.
5. Go back to map screen.
6. When you want to stop recording track tap on gray stop button in the middle of right edge of GPX Viewer PRO screen.
7. Confirm dialogs and proceed to dialog where you can choose File type, choose your preferred file type and tap on OK button.
8. After exporting track into your preferred file format tap on red recording button in the middle of right edge of GPX Viewer PRO screen.
9. In shown dialog tap on Export button.
10. Confirm dialogs and proceed to dialog where you can choose File type, choose your second preferred file type and tap on OK button.